Japanese Pension and Social Security - I am not an expert on Japanese National Pension or Social Security, so please do not take anything on this page as authoritive. These are a few things that you may want to investigate further.
Social Security:

Please go to the SS home page: http://www.ssa.gov/ to check for yourself any information provided here. You can get your SS history and estimated retirement and survivors benefits statement from this site.

After you receive your history calculate your estimated benefits by using their online calculator at: http://www.ssa.gov/planners/calculators.htm

Be sure to take into account the Windfall Elimination Provision because your future benefits may be lower than that shown on your history and benefits statement. Also, if you are short of the forty quarters (10 year) pay in requirement please see Totalization Agreement elsewhere in this section.

Japanese Pension:

I am told that you have to pay in 20 or 25 years into this system in order to get any benefits. However, I went to the Shakai Hoken Jimusho and confirmed that, because of my age when I entered the system, I only had to pay in for 14 years and 3 months. You may want to check this out for yourself. See Totalization Agreement below.

If you leave Japan before qualifying for benefits, I understand that you can apply at an overseas Japanese consulate to get a refund of some approximation of 3-5 years worth of the premiums that you have paid, subject to some maximum. I don't know how this has changed with the Totalization Agreement . It may be that after leaving Japan, you may not want the refund as under the Agreement, you may qualify for a pension from Japan based on your contributions. For example if you paid in for 15 years it may be better to get a pension based on 15 years of contributions rather than a refund of only 5 years contributions. I have no idea how the Japanese government will enact provisions in this respect.

Totalization Agreement:

This Agreement went into effect on October 1, 2005. The biggest effect on my clients is that it provides that the minimum required pay-in period (25 years in Japan and 40 quarters (10 years) in the US) can be met with pay-in periods in the other country. So even if you work only 3 or 4 years in Japan, you may qualify for a Japanese pension if you meet the Japanese (25 year?) requirement by counting years that you paid into the US social security system. The pension is likely to be very small, but every American who has ever paid into the Japanese Pension system should be aware of this. The Agreement does not address the issue of qualifying for US Medicare insurance.

Things you should do:

1. Contact any American friends who have left Japan to let them know about this Agreement.

2. Keep your little Japanese pension book FOREVER.

3. If you know of anyone who has left Japan and is applying for the 3-5 year refund of Japanese pension payments, you may want to tell them about this. I have no idea if the unrefunded portion of contributions will qualify for a Japanese pension. The person may decide that a Japanese pension at retirement age is better than the partial refund of contributions now.

4. If you are working private jobs in Japan purposefully to pay into US social security for 40 quarters (10 years) as a self-employed person, this may not be necessary under the Agreement. Your period of payment into the Japanese Pension System may satisfy this test.

5. It is important to be aware that the Agreement does not relate to US medicare benefits at age 65. If you plan to retire in the US and qualify for medicare, you still need to have 40 credits (ten years) of payments into medicare